The present invention relates to a variable magnification imaging device for a copying machine which has a lens and a mirror disposed one after the other in an optical path which terminates at a photoconductor.
A variable magnification imaging device for the above-mentioned application includes a lens assembly and a mirror assembly disposed in an optical path which extends from an original document on a transparent platen to a photoconductor. Various systems have heretofore been proposed to attain a plurality of alternative magnifications: shifting the lens and mirror assemblies to a desired magnification position, varying the focal length of the lens assembly while shifting it, or selectively using different lenses for different magnifications while shifting the mirror assembly or using another mirror assembly. In this type of imaging device, the mirror assembly is guided by rods to slide therealong to a predetermined position when the magnification is to be changed.
However, the imaging device with the slide type mirror assembly requires a substantial driving force to perform reciprocation between different magnification positions. The inherent position of the mirror assembly limits the accessibility thereto and thereby makes it difficult to clean or otherwise maintain the mirrors. Moreover, the slide mechanism for the mirror assembly has to be machined and assembled with significant accuracy at the sacrifice of costs.